This application relates to a controller for managing the DC-DC Converter and Power Management Unit (xe2x80x9cConverterxe2x80x9d) previously disclosed by Sustainable Energy Technologies (xe2x80x9cSETxe2x80x9d) in U.S. Provisional Patent Application Serial No. 60/221,596, filed Jul. 28, 2000, U.S. patent application Ser. No. 09/917,256, filed Jul. 27, 2001, and International Application No. PCT/US01/23681, filed Jul. 27, 2001, the contents of which are hereby incorporated by reference. It also relates to a controller for managing other DC-DC converters, as well as AC-DC or DC-AC inverters.
According to various aspects and embodiments of the present invention, an interface between software and hardware to control a DC-DC converter or an AC-DC or DC-AC inverter is provided. Fuzzy logic control algorithms are also provided. Although a presently preferred algorithm is described herein, any control algorithm that provides the needed output control signals to the hardware can be used.
In one embodiment, designed for use with a DC-DC converter that permits bi-directional current flow, a control circuit receives commands from a control logic to operate a converter in one of four modes including boost right, buck right, boost left, and buck left modes. The control circuit also receives two modulating signals that are used to control the operating voltages and current in each of these modes. The inputs from the control software are translated into gate drive signals that operate power electronic gates included in the DC-DC converter design.
Control variables can be used as inputs to the control software. Various control modes are possible for each of the control variables. For example, each variable can be configured to operate freely with no constraints; operate freely within specified limits; maintain a specified set point; or track a variable analog input signal. The control logic can also provide for fuzzy prioritization of the demands for the different variables. If the converter/inverter cannot simultaneously meet the demands placed on two variables, it can choose the more important constraint.
A controller configured according to the principles of this invention can be used in various applications, including in conjunction with a step wave power converter in fuel cell systems and other systems that include a variable power source and a battery. The controller can also operate independently as the interface between two DC power systems, such as in telecommunications or automotive applications. In these cases, the interface would generally be between a variable power source and a fixed voltage DC distribution circuit backed up by a battery.
Some important features available through converter/inverter control using the principles of the present invention are described below. Among other things, flexible fuzzy logic software allows easy configuration for use in different applications, and allows for complex control constraints and strategies to be easily implemented and fine-tuned. For instance, a DC-DC converter can be controlled to perform maximum power point tracking as long as the control variables stay within their specified ranges. These ranges and the maximum power point tracking control parameters can be configurable independently.
In addition, proper control of a converter/inverter allows it to respond extremely quickly to changes in current demand while controlling other variables. The flexibility provided further allows the same power conversion hardware (converter/inverter) to be used in either the parallel (resource bus) configuration or in the series (battery bus) configuration, by simply interchanging the connections of the battery and the resource to the system. This allows a single product to be developed that can be used in either the resource bus or battery bus configuration; whichever is preferable for the given application.